Hitherto, in the dental remedy, in the case of diseases where esthetics are required as in the case of inlays, crowns, and the like, filling restoration by a dental composite resin, or restoration by a dental prosthesis such as ceramic inlays, resin facing cast crowns, porcelain bonded facing cast crowns, and all ceramic crowns, has generally been employed.
The filling restoration by a dental composite resin is usually applied in the case of inlays and it is a restoration method in which a dental composite resin directly filled in a tooth cavity is polymerized for curing in the cavity by chemical polymerization or photo-polymerization. On the other hand, the restoration by a dental prosthesis is a restoration method in which after preparation of a cavity or preparation of an abutment tooth die, an impression (an tooth counterdie) is taken, a plaster model (a tooth duplicate) is prepared on a basis of the impression thus taken, a dental prosthesis is prepared on a basis of the model thus-prepared in the following manner, and the thus-prepared dental prosthesis is then setting to the tooth by using a dental cement.
In the case of dental prostheses such as resin facing cast crowns or porcelain bonded facing cast crowns, these dental prostheses are prepared in a process in which a wax pattern of a core part is prepared on a plaster mold by using a wax in a lost wax casting method, the wax pattern is invested in a refractory investment, after curing the investment, the assembly is heated in an electric furnace to burn out the wax pattern, a metal is cast in a thus obtained mold, the resulting cast material is excavated from the investment, which is then cut and polished to prepare a metal core, and then, a hard resin for crown and bridge is built up and polymerized, or a porcelain is built up and burnt, in a core part of the thus obtained metal core.
In addition, in the case of dental prostheses such as ceramic inlays or all ceramic crowns, these dental prostheses are prepared in a process in which a duplicated model is prepared by using a refractory model material, a ceramic raw material is built up and burned on the thus-prepared duplicated model, the refractory duplicated model is eliminated, and then, trimming and polishing are then carried out.
However, in the case of a dental composite resin, since this process is one in which the dental composite resin in a paste-like form is polymerized for curing in the cavity, unpolymerized monomers inevitably remain, leading to a problem in pulp irritation.
In addition, in the case of dental prostheses, although as described above, complicated operations are required for the preparation of dental prostheses, this process is widely employed. However, since not only the shape in an oral cavity or the site in which a prosthesis is to be prepared is different individually, but also an extremely high precision in a several Atm order is required in the finished dental prosthesis, a skill of a dental technician along with a long period of time and a high cost is required.
Under these circumstances, as a method by which a dental prosthesis with a constant quality can be supplied within a short period of time and in a stable manner in recent years, a CAD/CAM system in which a dental prosthesis such as crowns or bridges is designed on a display by utilizing a computer has been drawing the attention, and a design and preparation system of dental prostheses by using such a CAD/CAM system represented by a Cerex system (by Siemens AG, Germany) is now commercially available. This system is a system in which a dental prosthesis is milling out of a ceramic block as a material to be grinded. However, according to this system, since the ceramic per se is hard, the finished dental prosthesis leads to a fear of likely wearing off the antagonistic enamel.